You are answering question with questions - that is impolite.
What to drive it with - any (decent) opamp buffer will do.
Any more explanations for declaring this "very very wrong" - perhaps some argumentation?
Would you set the input impedance of your preamplifier to 2.2K? Why or why not?
There are good reasons to set the input impedance of a line level circuit. What is the good reason for setting it so low here?
I think a couple of those circuits were lifted from a larger modular or integrated design, where there were good reasons to set the input impedance there.
The question is intended to make you think. Answer the question or say "I don't Know" and we can proceed.
We might be through. Curb the attitude.
I gave you reasons. If you don't like them, OK.
Nope, your statement was definitive, you are unable to justify this.
Admit it and we can move on.
I can justify it. Why should I help you after you've been so rude?
Why even come here and ask questions? This isn't Twitter son.
It would depend on the preceding stage, as I have said so it's pointless to second guess the designer's aims and also, we don't have the full schematic.
Of course. And without specific input from the OP any attempt at helping them would be second guessing.
One of the circuits was a buffered control already, and all that needed to be done to make it a turnkey circuit was to change a couple of resistors. You could have had a complete stand alone turnkey circuit. OP suggested buffering the buffer, which would work but the same result could be achieved by swapping resistors.
It's easy to take classic circuits and improve them with today's parts. And there's a way around virtually every shortcoming in many circuits. To me these things are obvious now but I clearly remember not being able to figure out why my circuit didn't work, or why they fell short of specifications, etc. I want to help people develop these skills now, but I can't force them.
I've been experimenting a lot with various tone controls, hard wired equalizers, higher order filters, crossovers, etc with great (but slow) success. This is the accumulation of decades of research and experimentation. I give a lot of people credit for helping me along. There's no shame.
One of the schematics uses a 4558 at a gain of 100. This should be replaced by at least a 5532 op amp.
The 4558 does make a great unity buffer.
The 4558 does make a great unity buffer.
That's one of the issues when using other people's designs. Line level circuits never need a gain of 100! Even a power amplifier has a typical voltage gain of about 27, give or take.
Sorry for resurrecting old thread (new member, can't DM yet) but did anyone ever take you up on this kind offer? If not I would definitely like to do so!!
Yes I still have it. I'll dig out the parts as I have moved home and they are spread over various boxes. I'll send you some photos of what I have by private message.
Can you share how you got that graph.
Im testing various tone control boards and multi band EQs.
It would be nice to see a chart like that.
Take frequency response measurements with RMAA with one band regulator at max position at a time.
Then select ("tick") these measurement sets and they will be shown in overlay mode (on top of each other).
NB! This display is a combination of independent measurements, when you maximize more than one control then resulting graph will be different.
I just walked one forum member through setting up the RMAA, I would rather not start repeating myself here:
https://www.diyaudio.com/community/threads/aiwa-aa-8300-restoration-ideas.396261/
Then select ("tick") these measurement sets and they will be shown in overlay mode (on top of each other).
NB! This display is a combination of independent measurements, when you maximize more than one control then resulting graph will be different.
I just walked one forum member through setting up the RMAA, I would rather not start repeating myself here:
https://www.diyaudio.com/community/threads/aiwa-aa-8300-restoration-ideas.396261/